Don’t be fooled…West Nile is still a threat to all of us

Don't be fooled…West Nile is still a threat to all of us
This is a favorite time of the year for many people, especially those who like sleeping with their windows open. The dogs of summer are behind us, football season has begun and it won't be long before farmers will harvesting this year's crop during South Dakota's biting cool autumn.

It's also a time to get lulled into complacency about things we normally watch for in the summer. It's not quite as buggy out as it used to be, but that's no reason to ignore precautions about West Nile Disease.

Ray Decker reminded all of us here at the Plain Talk of this fact last week, when he stopped by our office to report his wife, Pam, had been hospitalized here in Vermillion after being diagnosed Aug. 29 with West Nile. We wish here a full, uneventful recovery.

Ray thought it would be a good idea for us to spread the word that West Nile is still a threat. We'd certainly have to agree with that assessment, especially after reviewing a recent media release we received from the South Dakota Department of Health.

South Dakotans who plan to head outdoors need to take precautions, according to a state health official.

"With schools back in session it's tempting to think summer is over and there's no need to worry about mosquitoes anymore," said Dr. Lon Kightlinger, state epidemiologist for the Department of Health. "However, cases are still being reported and we know that transmission is still taking place so now is not the time for people to stop protecting themselves. Until we have our first hard freeze, West Nile will remain a threat."

The department recommends the following steps to reduce the risk of WNV: �

  • Don't give mosquitoes a place to breed. Get rid of old tires and other containers that accumulate water, regularly change water in bird baths and outside pet dishes, and drain water from flower pots and other garden containers.
  • Limit your time outdoors at dusk and dawn when mosquitoes are most active.
  • Use mosquito repellent containing DEET, Picaridin or oil of lemon eucalyptus. Limit exposure by wearing appropriate clothes.

    "Local control programs across the state are working hard to reduce mosquito numbers in our communities. It's important that each one of us also take personal responsibility to protect ourselves and our loved ones from mosquito bites," said Kightlinger.

    Since 2002, South Dakota has reported more than 1,500 cases of WNV, including 23 deaths.�So far in 2007, there have been 107 cases of human West Nile and three deaths.

    Here are some more facts to consider:

    Although West Nile Virus can be transmitted at any time of day, 10 p.m. to 2 a.m. are the hours in which the mosquitoes that spread West Nile Virus are most often on the prowl for blood.

    SDSU professor Mike Hildreth, a research parasitologist in SDSU's Department of Biology and Microbiology, said that is one of the findings emerging in SDSU's mosquito research this summer.

    Ongoing research by Hildreth and his SDSU colleagues in cooperation with the South Dakota Department of Health is making it easier to protect human health against West Nile Virus.

    Although South Dakota has about 43 species of mosquito, Hildreth said a species called Culex tarsalis is the primary vector of West Nile Virus in the state.

    Research at SDSU has previously shown that Culex tarsalis fares well even in drought years, just as in other western states; that Culex tarsalis prefers to breed in flat, grassy lowlands that are temporarily flooded after rainfall events; and that the month of August is generally the most dangerous month in South Dakota for transmission of the virus.

    This summer, Hildreth's graduate student, Matt Wittry, is using a trap that fools mosquitoes into thinking they will get a blood meal. The research tries to pin down the high-risk times of day for transmission of the virus in South Dakota.

    "We have what's called a rotator trap and it rotates the collection cups every two hours. We have been using the rotator trap to collect mosquitoes every two hours," Hildreth said. "From that we know that generally from about 10 p.m. to about 2 a.m. is the time at which Culex tarsalis, that vector mosquito, is biting most frequently."

    munities that it's important to spray around areas such as ball diamonds if they are still in use during high-risk times.

    SDSU Extension Pesticide Education Coordinator Jim Wilson added that Hildreth's research, relayed by SDSU Extension professionals and the South Dakota Department of Health, is already providing practical guidance for those who carry out mosquito control campaigns across South Dakota. Many communities around the state have reported delaying their ULV mosquito fogging applications until later in the evening in order to more effectively control mosquito populations and reduce the potential for West Nile Virus transmission.

    Spraying for adult mosquitoes is only one aspect of mosquito control efforts in South Dakota. Communities also are establishing buffer zones around communities and treating Culex tarsalis larval habitats in those buffer zones.

    Hildreth said some of SDSU's work is based on a California study of Culex tarsalis' feeding habits, and reaches essentially the same conclusions, despite the differences in geography.

    This year's work at SDSU also will look into whether the vector mosquito's feeding habits vary with temperature. Scientists still don't know if Culex tarsalis is cued by temperature, by daylight, or by some other factor.

    SDSU's work this summer also will be looking at how well Culex tarsalis populations will rebound after recent rains in parts of South Dakota. Until those rains, it appeared that the vector mosquito populations had already peaked in several areas of the state.

    SDSU's mosquito research may be of benefit to neighboring states such as North Dakota, Nebraska, Wyoming, and Montana, which have similar conditions for Culex tarsalis. In addition, Hildreth said, southwestern Minnesota has a fairly high population of Culex tarsalis.


    To learn more about WNV prevention, visit the Web site at

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